US smoking patterns are changing dramatically: non-daily, or intermittent smokers (ITS), now comprise a quarter or more of all adult smokers in the US and are rising dramatically. ITS suffer serious smoking- related morbidity and mortality, yet DHHS guidelines underscore the distinct lack of evidence to guide therapy for this group. Moreover, the role of nicotine in ITS' smoking behavior is not well established. Our group's intensive study of ITS revealed the paradoxical nature of their smoking: they voluntarily abstain for days at a time without evidence of craving or withdrawal symptoms, yet ITS also exhibit signs of nicotine dependence. Our analyses of national data demonstrate that ITS have trouble quitting: Although they make more efforts to quit than regular daily smokers (DS), ITS trying to quit have failure rates of up to 79%- almost as high as those of DS-and also seek out quit aids, including medications. A substantial portion of ITS are at risk of graduating to daily smoking long term. Our own primary data further show that ITS' smoking is driven by stimulus control - exposure to specific, often idiosyncratic, stimuli and situations that prompt smoking (e.g., social venues, stress). This suggests that re-exposure to such stimuli may play a large role in relapse among ITS, and that ITS may benefit from acute doses of nicotine in those situations. Oral nicotine medication such as nicotine gum, which we have shown to reduce acute cue-provoked craving in daily smokers, is ideally suited to provide such acute 'rescue' treatment. Our overarching aim is to study the effect of as-needed oral Nicotine Replacement Therapy (NRT) - 2 mg nicotine gum - for smoking cessation in ITS, and to study their process of relapse using Ecological Momentary Assessment (EMA). Reviews of ITS have called for research on ITS' relapse process, and for evaluation of cessation methods, including medications, among ITS. Yet no study to date has examined the cessation or relapse process in ITS, or tested the use of NRT in this population. We propose a double-blind, randomized, placebo-controlled trial of oral NRT for smoking cessation in ITS. 600 eligible ITS interested in quitting will be recruited through multiple channels, enrolled, and randomized 1:1 to active NRT vs. placebo. Participants will attend 6 sessions with brief behavioral support, with a planned quit day at week 2. Long term abstinence will be assessed and biochemically validated. EMA data collection spans two weeks of ad lib smoking and 6 additional weeks following the quit date, to capture data on craving, withdrawal, and relapse among ITS, and relate relapse contexts to baseline smoking patterns. Developing a better understanding of ITS' smoking and of how to help them quit is essential to public health: it will not only assist a substantial fraction of hitherto-ignored smokers, but also strategically anticipate upcoming scientific, treatment, and public health needs that will arise if the proportion of ITS continues to grow. Further, assessing the effect of nicotine medications on ITS' quitting will shed light on the role of nicotine in ITS' smoking and difficulty quitting. .